The stress-induced morphological instability of an interface is examined with the recently developed phase field crystal (PFC) approach. Our results show that the interface width, generally assumed to be zero thickness in classical theory, is a crucial length scale for phenomena at the nanoscale. We find that the critical wavenumber of the instability deviates from the prediction of the continuum theory when the length scale of the instability is on the order of the interface width. In addition, we find that large stresses induce nonlinear elastic effects that alter both the wavelength of the instability and the interfacial morphology. This nonlinear elastic effect is generic and thus will be observable during heteroepitaxy. Finally, we show that the diffusional dynamics employed in the PFC model can capture quantitatively the stress field that accompanies the diffusional evolution of interfaces.

• Received 19 May 2009

DOI:https://doi.org/10.1103/PhysRevB.80.125408